1. Field of the Invention
The invention relates to an electrochemical storage cell of the sodium and sulfur type with at least one anode space for receiving the anolyte and a cathode space for receiving the catholyte which are separated from each other by an alkali ion-conducting solid electrolyte and are bounded at least in some regions by a metallic housing.
2. Description of the Prior Art
Such rechargeable electrochemical storage cells with solid electrolyte are highly suitable for the construction of storage batteries of high energy and power density. The solid electrolytes used in alkali/sulfur storage cells, which are made, for example, of beta-aluminum oxide, are distinguished by the feature that the partial conductivity of the mobile ion is very high and the partial conductivity of the electrons is smaller by many powers of ten. By using such solid electrolytes for the construction of electrochemical storage cells, practically no self-discharge takes place since the electron conductivity is negligible. Also, the reaction substances cannot pass as neutral particles through the solid electrolyte.
A special example for such rechargeable electrochemical storage cells are sodium/sulfur storage cells which have a solid electrolyte of beta-aluminum oxide. For these storage cells there are two embodiments: the so-called "normal storage cell" and the "inverted storage cell". The difference between the two storage cells is brought about by the different arrangement of the two reactant spaces. In the first-mentioned sodium/sulfur storage cell, the anode space is located inside the solid electrolyte, while the cathode space is arranged between the solid electrolyte and the metallic housing of the storage cell. In contrast thereto, the cathode space in the inverted storage cell is within the solid electrolyte, while the anode space is arranged between the metallic housing and the solid electrolyte. A very great advantage of these inverted sodium/sulfur storage cells is that they have substantially better corrosion resistance than the abovementioned normal sodium/sulfur storage cells. This advantage is offset by the disadvantage that these inverted storage cells of conventional design have less capacity than normal storage cells for the same mechanical design and size of the solid electrolyte. This, in constructing a battery from inverted storage cells to obtain a desired energy content, the number of storage cells must be larger than the number of normal storage cells to obtain the same energy content.